Surround to Stereo channel mapping

Posted by: sbilotta on 09 January 2010

Hi,
wondering if anybody can shed some light: I am remapping HiRes surround (quad or 5.1) audio files to HiRes stereo, to be played on my system.
In doing so, and not wanting to loose any audio info, I am currently mapping the surround channels as below:
- Quad: Left channel as Lf + Ls
Right channel as Rf + Rs
- 5.1: Left Channel as Lf + Ls + 50% Center + 50% Sub
Right Channel as Rf + Rs + 50% Center + 50% Sub

Is this correct to get a "standard" stereo quality/imaging playback ?

Many thanks
Stefano
Posted on: 09 January 2010 by Aleg
quote:
Originally posted by sbilotta:
Hi,
wondering if anybody can shed some light: I am remapping HiRes surround (quad or 5.1) audio files to HiRes stereo, to be played on my system.
In doing so, and not wanting to loose any audio info, I am currently mapping the surround channels as below:
- Quad: Left channel as Lf + Ls
Right channel as Rf + Rs
- 5.1: Left Channel as Lf + Ls + 50% Center + 50% Sub
Right Channel as Rf + Rs + 50% Center + 50% Sub

Is this correct to get a "standard" stereo quality/imaging playback ?

Many thanks
Stefano


No that's not correct.

This is really difficult stuff with different percentages and with phase shifts coming into play. There are all kinds of matrices for converting surrond-sound to stereo. Do some searches on HydrogenAudio forum, and get scared Eek.

Best to use Sox or dBPowerAmp converter to reduce the channel count and see which one you like best.

Don't use eac3to for this, it gives a wrong conversion with to much emphasis to the left channel.

-
aleg
Posted on: 10 January 2010 by sbilotta
OK... yes I see your point on the matrices and ratios, but how about a more simple approach then like what DSP plugins in Foobar and DBPoweramp do a good job in channel mixing, and in particular from surround to stereo ?

Any experience on this ?
Posted on: 10 January 2010 by Aleg
I only used the foobar plugin for replay on my PC, it is good enough for that but my PC doesn't have Hifi grade audio components.

For replay on my Naim set I tried both Sox and dBPoweramp, there is some difference in width of the soundstage but I haven't decided on my favourite between those two. That might also depend on the genre of the music. That's really the reason I said "try both and see which you prefer".

You also might have to adjust the volume of the conversion result, so after conversion normalise to your prefered level. With dBPoweramp you can do that in one go. dBPoweramp has of course a much nicer, easier user rinterface. Sox is only command line, but that doesn't put me off.

Overall I think you can get reasonably good conversion results for surround and quattro.

-
aleg